Centrifugal liquid deaerators have been utilized in hydraulic systems over a prolonged period of time. In the course of operation of many hydraulic systems, air becomes entrained in the hydraulic fluid. The presence of entrained air may cause a number of difficulties in system operation, a foremost being "cavitation" which can damage parts of the system. Another problem brought about by the presence of entrained air is what may be termed "sponginess". In hydraulic systems, the hydraulic fluid is typically regarded as incompressible and the system designed about that premise. However, when a gas such as air becomes entrained in the fluid, it adds a perceptible measure of compressibility to the fluid so that system actions are not as positive, i.e., become spongy, as a result of compression and/or expansion of the entrained gas due to system pressure changes.
Deaerators then, have been employed to rid systems of these and other deleterious effects of entrained gas in hydraulic fluid. More recently, where centrifugal deaerators have been employed, the deaerator may also act as a boost pump to charge a fixed displacement pump or provide deaerated lubricant and/or coolant to components parts of the systems at relatively low pressure. In general, such centrifugal deaerators and pumps take on the form of a generally cylindrical housing which is mounted for rotation about its cylindrical axis. Liquid to be degassified is directed into the housing, generally on its axis at one end of the housing while the housing is spinning about its axis. Axially extending blades within the housing cause the entering flow to rotate with the housing.
At locations remote from the liquid inlet, the cylindrical wall of the housing is provided with a plurality of deaerated liquid outlets. On the housing axis opposite the inlet is an axially directed gas outlet.
Because the liquid will have a higher density than the gas, the centrifugal force imparted to the mixture during rotation of the housing will cause the liquid to move radially outwardly to form an annular body of liquid within the rotating housing. The head in the annular body of liquid will drive any entrained gas out of the liquid and such gas will move radially inwardly towards the axis, being less affected by the centrifugal force as a result of its drastically lesser density.
Consequently, the liquid may travel axially within the housing from the inlet to the outlets in the cylindrical wall of the housing to be expelled therefrom under some pressure by reason of the centrifugal force acting on it. This factor allows the deaerator to be used as a boost pump. At the same time, the body of gas within the annular body of fluid will move axially within the housing to the gas outlet as it is being continually displaced by additional gas entrained in incoming fluid.
While such constructions have worked well for their intended purpose, it is desirable to improve their efficiency. The present invention is directed to providing such an improvement.